Conventional primer systems for use with moisture curable sealant compositions generally contain a large amount of volatile organic solvent, a film former, pigment and silane coupling agent. The coupling agent is typically an aminosilane, mercaptosilane, or isocyanatosilane which reacts, for example, with free isocyanate groups in the sealant and with free hydroxyl, oxide, or silanol groups on the substrate to form a bridge between the sealant and the substrate. The conventional sealant primer systems provide good adhesion across the substrate-sealant interface and are convenient to use because they dry quickly. However, recent concern over the emission of volatile organic compounds (VOC) into the environment has resulted in pending legislation which would essentially mandate the elimination of volatile organic compounds whenever possible.
In addition to the problems relating to compliance with pending VOC legislation, the use of conventional solvent based sealant primer systems requires the implementation of precautionary procedures and the incurment of potential risks due to the toxicity and flammability of the organic solvents. Accordingly, organic based sealant primer systems are undesirable and an aqueous based sealant primer system which has a substantially reduced organic solvent content or which is preferably free of volatile organic compounds, and which provides comparable adhesion across the substrate-sealant interface, would be highly preferred.